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Ok so it is time to get new rotors/pads and I have been researching what to purchase. I have read through quite a number of threads here but have yet to come to a conclusion. What exactly are the benefits of slotted or drilled rotors compared to OEM? Here are a couple tidbits of info I came across while searching:

Directly off of UUC's website..."Slotting: there are many reasons to slot rotors. Primarily, slotting aids in removal of water and debris on the rotor surface, evacuation of hot pad "off gassing" vapor, and provides a visual wear indicator.

Details: These slots do not extend all the way to the edge of the rotor for a very specific reason; this maintains the structural integrity of the rotor. Other brands with slots all the way to the end have created "stress risers" where cracking may develop. No such problem exists with this design. Additionally, directional slotting enhances effectiveness.

NO DRILLING! Drilled holes in rotors often used for "show" are prone to cracking and catastrophic failure. The holes create stress risers which will lead to this sort of failure. Additionally, drilled holes do not improve cooling, rotary-vane rotors lose efficiency when drilled because cooling air does not not pass through the rotor circumferentially but is instead prematurely evacuated by the holes.. "

Hmmm if cross drilled rotors do no improve cooling and are prone to failure then why would any BBK use them?

Also here is more info found when scanning ebay (link below)..."Brembo OE "blank" rotors offer better performance than Cross-drilled rotors. Cross-drilled rotors might look "cool", but what are they really doing for performance? Brake rotors were first "drilled" in the 40's and 50's because early brake pad materials gave off gasses when heated to racing temperatures, which is called "gassing out". These gasses then formed a thin layer between the brake pad face and the rotor, effectively lowering the coefficient of friction. The "cross drilled" holes were implemented to give the gasses a place to escape. Today's brake pad materials do not exhibit the same gassing out problems as these early (old) pads. Also, there are many companies that sell "cheap" cross-drilled and slotted rotors. They do this by purchasing Brembo blanks and having them cheaply altered by a third party. Doing this sacrifices the rotors structural integrity, and can be a huge safety risk. If you contact Brembo, they will not recognize these discs after they have been altered. These rotors are known to crack and warp very quickly. If you want the actual Brembo cross drilled and slotted rotors you will be paying much more. That's why these blanks are perfect; they perform better, do not tear through pads, are priced much lower, and are much safer."http://cgi.ebay.com/ebaymotors/Bremb...87492957QQrdZ1

If you have to go with something "fancy" then go slotted, the general idea behind them is sound, while the driled are really just for show. They will wear your pad faster (think of a cheese grater). Personally im just a daily street driver so Iwent with the standard OEM rotors and have been happy. But it all comes down to what makes you happy, if you want to have a nice set of good looking rotors then get the drilled or slotted (slotted being my choice of the two).

NO DRILLING! Drilled holes in rotors often used for "show" are prone to cracking and catastrophic failure. The holes create stress risers which will lead to this sort of failure. Additionally, drilled holes do not improve cooling, rotary-vane rotors lose efficiency when drilled because cooling air does not not pass through the rotor circumferentially but is instead prematurely evacuated by the holes.. "[/COLOR]

Hmmm if cross drilled rotors do no improve cooling and are prone to failure then why would any BBK use them?

Excellent question!

The rotors we use in the big brake kit are genuine BMW Motorsport rotors, which are apparently cast-perforated, not actually drilled.

The difference is that the holes are cast into the rotor, so the metallic grain structure (and therefore the strength) is not compromised as with conventional drilling.

Please note that we are in the process of updating our website pricing on brake rotors.

I think that you will find our new Gen2 black rotor regular pricing is better than "group buy" pricing for other brands.

Please see: http://www.uucmotorwerks.com/rotors/ and click on your application for options. Please note - not all applications updated yet, if your listing does not show all options, please call us for pricing!

Remember too, that when you see all those race cars sporting drilled rotors, its because they consider it a good track weekend if they last FRI, SAT, SUN. Rotors and brake pads are disposable items to a race team and they include that in their track weekend budget.

The typical street driver wants longevity from their rotors, a long-lasting pad that is quiet and doesn't eat the rotors up quickly, and brakes that don't squeal or rattle. This is what BMW gives you in OEM products.

Rob@UUC and I go wayyyyyyy back, over 10 years playing with BMW's, don't we buddy? The only 'holed' rotors that we'd run on our cars are the ones that are cast in the formation process (such as what comes standard from Porsche AG).

If you want the look of a more 'racy' rotor, then go slotted from UUC.

Drilled or slotted rotors will chew through pads faster, and any performance improvement is sketchy at best. My opinion is that the best performance is found with blank rotors and high performance pads.

That said, I have run the cheap drilled rotors with Axxis Ultimate pads before, and had great braking performance and no warping or cracking issues. As said above though, pads wore out much faster, and the rotors cannot be turned once they are grooved. It looked nice, but I'll stick with OEM rotors from here.

Drilled or slotted rotors will chew through pads faster, and any performance improvement is sketchy at best. My opinion is that the best performance is found with blank rotors and high performance pads.

Not quite. "Performance" is more than just 60-0.

In real-world use, slotted rotors provide additional benefits in water (rain) evacuation from the surface, and pad freshening to reduce glazing/squealing.

Additionally, they serve as a useful visual wear indicator... when the slots are gone, time to replace rotors!

Quote:

That said, I have run the cheap drilled rotors with Axxis Ultimate pads before, and had great braking performance and no warping or cracking issues.

Then you're not using them hard.

Axxis pads, despite the marketing, are not "enthusiast" pads. They are very hard pads, and we've seen many instances of premature wear and surface cracking.

We test as many pads as possible so that we can offer our customers the best choices for their needs. I wish we found Axxis suitable, great profit margin!

My motto is don't buy more than you need. So, for the street it's plain rotors and good pads like Axxis metal masters. Fashion fads are another thing altogether. Just don't confuse fashion with function! I do have ATE slotted disks on my wifes Audi because she's a lite braker and the slots help even out the wear. Which brings up an interesting point on wheel size. Anything over 18" and less that 45 aspect ratio is the same thing=fashion fad. If the fashion fad is race car like drilled rotors why isn't the fashion fad Forlmula 1 like small wheels and big tires? There's no predicting those fashion fads!

I believe all the hype about drilled rotors...but I went with a cross drilled/slotted combo from IRotors.com anyways and completely satisfied so far.

After 8 months they are still in great condition. Can barely even tell that they have worn at all. I would have went with a Brembo rotor, but unfortunately they don't make em for the E46 M3.

I still find it hard to believe that the drilled are dangerous. Mercedes, Audi, Porsche, BMW, and any sports car use em. After reading this thread I guess they are all done the proper way though. Every BBK (Brembo, Stoptech, Wilwood, Rotora, etc) all use em. The question is how are they made....

I still find it hard to believe that the drilled are dangerous. Mercedes, Audi, Porsche, BMW, and any sports car use em. After reading this thread I guess they are all done the proper way though. Every BBK (Brembo, Stoptech, Wilwood, Rotora, etc) all use em. The question is how are they made....

Marketing is amazing in what it says and what it does not say so clearly...

Stoptech very specifically does not recommend their drilled rotors for track or race use.

Please read what I wrote about about cast-perforated versus drilled rotors. An aftermarket drilled rotor is definitely not the same as the OE rotors.

What exactly does "cast-perforated" mean?
Are the holes cast clear through entire, as a pilot, as a dimple, or something else?
What, if any, machining takes place on the holes after casting?

...

Quote:

Originally Posted by Rob Levinson * UUC Motorwerks

The rotors we use in the big brake kit are genuine BMW Motorsport rotors, which are apparently cast-perforated, not actually drilled.

The difference is that the holes are cast into the rotor, so the metallic grain structure (and therefore the strength) is not compromised as with conventional drilling.

Holes are holes - all the way through. Not dimples.

Normal post-casting cleanup maching takes place, no different than any other rotor... the rotor face, edges, inner and outer hub faces, and casting flash within the holes. When you look at a rotor, every surface that is not rough has been machined.

Well, if you want the rotors just for looks, and not performace go for it. Dont think you will be cracking them, unless you drive your car hard. I got the brembo sloted/drilled, have not given me any trouble. But for performace or auto X i would go with just slotted.